In general, laser beams can be shaped by directing the output of a laser through one or more beam shaping optics, such as diffractive optical elements, lenses, mirrors, prisms and the like. Depending on the specific laser beam profile desired, the effect of the shaping can include homogenizing the beam's intensity across the beam's width, or ensuring a particular cross-sectional shape to the beam (e.g., circular, rectangular, elliptical) and/or ensuring a particular beam intensity profile within the beam's cross-section. Laser beams can also be actively shaped, e.g., using spatial light modulators (SLMs). For example, a reflective or transparent SLM, composed of an array of elements whose reflective or transmissive properties are independently variable, can be positioned in the path of the laser beam and operated to variably change the beam profile by control of the SLM. In many cases, the beam shaping optics are positioned outside of the optical cavity of the laser.